POS0390 PRIOR ANTIRESORPTIVE TREATMENT REDUCES LUMBAR SPINE BMD RESPONSE TO ROMOSOZUMAB IN CAUCASIAN POSTMENOPAUSAL WOMEN WITH SEVERE OSTEOPOROSIS
Authors: P. Ravji, M. Mcrorie, K. Berg, S. Ralston, B. Hauser
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Romosozumab, a monoclonal antibody against sclerostin, is a newly licensed dual-acting osteoporosis (OP) treatment for patients at very high fracture risk. Most patients included in the pivotal trials (ARCH[1] and FRAME [2]) were treatment naïve. However, many patients in day-to-day clinical practice who are eligible for anabolic therapy have been pre-treated with antiresorptive medications. <h3>Objectives</h3> Our aim was to analyse bone mineral density (BMD) treatment response to Romosozumab in patients with severe osteoporosis who are attending the osteoporosis clinic. A further objective was to analyse whether pre-treatment with antiresorptive osteoporosis medication (OPTx) influences the BMD treatment response at any BMD site. <h3>Methods</h3> Retrospective single-centre analysis of patients who have completed a 12-month course of monthly sc Romosozumab treatment (210mg) between February 2021 and November 2022. Local guidance recommends the use of Romosozumab in patients with severe spinal OP with at least two moderate vertebral fractures and OP at the hip as defined by DXA. BMD assessment was usually performed with DXA at baseline and after treatment completion. <h3>Results</h3> Out of 56 patients offered Romosozumab, 52 agreed to start treatment and 47 patients completed the full course of therapy. All patients were postmenopausal women with an average age of 73.1± 9.7 years and BMI of 24.4 ±7.1 kg/m<sup>2</sup>. The baseline 10% major osteoporotic fracture risk as calculated by FRAX was 32.2 ±13.5. Mean baseline BMD lumbar spine (LS) T-score was -3.8 ±1.0 and total hip (TH) T-score was -3.0 ±0.7. The vast majority (95%) of patients had a history of vertebral fractures and half of the patients (50%) had a history of an additional non-vertebral fracture. 31 (66%) patients were treatment naïve or had recent antiresorptive treatment for less than 6 months, the remainder of patients received recently mostly oral or parenteral bisphosphonate treatment. After 12 months the overall mean % change BMD at the LS was 14.1 ±9.4 and 5.7 ± 5.6 at the TH site. Spine BMD increase was significantly higher in treatment naïve patients than in patients who had previous OPTx over 6 months (17.3 ±9.0 vs 7.6 ±6.9; p&lt;0.01). Prior OPTx however did not seem to influence TH BMD response to Romosozumab (5.1 ±6.3 vs 6.1 ±5.1 in OPTxnaive patients) as shown in Figure1. Age (<i>r</i> =-.37 <i>p &lt;.05; Spearman's rho</i>) and prior OPTx (r= -.49 <i>p&lt;0.01</i>) are inversely related to LS BMD increase. Multivariate regression analysis including age, baseline spine BMD and prior OPTx identified prior OPTx as independent predictor (beta<sub>St</sub>= 0.422; p&lt;0.05) of spine BMD response to Romosozumab treatment. <h3>Conclusion</h3> The overall BMD response at LS and TH site after 12 months Romosozumab treatment in real world is similar to that reported in the ARCH trial. Pre-treatment with antiresorptive treatment seems to significantly dampen the BMD response at the lumbar spine, which highlights the importance of the choice of OPTx sequence. <h3>References</h3> [1]Saag KG et al.(2017) Romosozumab or Alendronate for Fracture Prevention in Women with Osteoporosis. N Engl J Med 377:1417-1427 [2]Cosman F et al (2016) Romosozumab Treatment in Postmenopausal Women with Osteoporosis. N Engl J Med 375:1532-1543 <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> Pollie Ravji: None declared, Morven McRorie: None declared, Kathryn Berg: None declared, Stuart Ralston Grant/research support from: UCB, Kyowa Kirin, AstraZeneca, Eli Lilly and Novartis, Barbara Hauser Speakers bureau: UCB, Chugai-Roche, Astellas, Effrx, Consultant of: Fresenius-Kabi, Celltrion Healthcare, Gedeon-Richter, UCB.